Lithium iron phosphate material, preparation method thereof and lithium ion battery

Abstract

The invention relates to a lithium iron phosphate material, a preparation method thereof and a lithium ion battery, the preparation method comprises the following steps: (1) mixing iron phosphide and first mixed powder, and sanding to obtain a doped precursor; (2) mixing a carbon source and the second mixed powder, carrying out secondary granulation, and roasting to obtain a coated precursor; and (3) mixing the doped precursor obtained in the step (1) and the coated precursor obtained in the step (2), and calcining to obtain the lithium iron phosphate material, wherein the step (1) and the step (2) are not divided into a sequence; the first mixed powder and the second mixed powder respectively and independently comprise phosphorus iron lithium mixed powder. According to the preparation method provided by the invention, organic combination of carbon coating and doping is adopted, the lithium iron phosphate material with excellent low-temperature performance and high compaction is obtained, and the problem that high volume density and low-temperature rate performance of lithium iron phosphate are incompatible is solved.

Description

technical field [0001] The invention belongs to the technical field of positive electrode materials for lithium ion batteries, and relates to a preparation method of a lithium iron phosphate material, in particular to a lithium iron phosphate material, a preparation method thereof, and a lithium ion battery. Background technique [0002] At present, new energy vehicles are hot, lithium-ion batteries are more and more used in power vehicles, and the performance requirements of batteries are also increasing. The promotion and wide-scale application of power batteries requires lithium-ion batteries with better safety and better performance. Compared with the short-life shortcomings of lead-acid batteries, the safety defects and high cost of ternary lithium-ion batteries are difficult to solve, and lithium iron phosphate batteries with relatively compromised or even advantageous performance in all aspects are even more advantageous. [0003] Lithium iron phosphate batteries als...

AI Technical Summary

Problems solved by technology

Although nano-scale materials have the characteristics of high gram capacity and high power, this energy density is mass density rather than volume energy density, that is, it cannot meet the strict restrictions on battery volume of electric vehicles

CN107482186A uses lithium manganate positive electrode material, which can realize the discharge capacity of -40°C and 5C. The low temperature performance of lithium manganate material is good, but the material itself is unstable, poor in high temperature stability, fast attenuation, and poor in cycle performance

[0007] The single high-compression material used in the above technical solution cannot satisfy the low-temperature rate performance well

[0008] CN 104377353A simply mixes carbon-coated nickel-cobalt lithium manganate and carbon-coated lithium iron phosphate in different proportions. Although the high-voltage performance of the obtained mixed material is better than that of lithium iron phosphate, the mixed material is still mainly Nickel-cobalt lithium manganese oxide is dominant, and the battery of this material has obvious material anisotropy, and the performance stability, cost and cycle performance of the mixed material have no obvious advantages

CN 105470559A uses lithium iron silicate, lithium iron borate, etc. to coat lithium iron phosphate materials, which can improve the electrical conductivity of lithium iron phosphate, and then improve the rate performance of lithium iron phosphate. However, the low-temperature rate performance of lithium iron phosphate as the core Can't improve effectively

[0009] The simple blending of materials in the above technical solutions cannot effectively guarantee the long-term stability of material properties

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